Radio detector



Jufiy 16, 1940. R WEAGANT 22117306 RADIO DETECTOR Filed May 11, 1938 M dMFl/F/EH l TUBE 1' INVENTOR ROY A. WEAGANT BY r ATTORN E Patented July 16, 1940 I e UNITED "STATES PATENT OFFICE 7 2,207,906 RADIO DETECTOR Roy A. Weagant, Douglaston, Long Island, N. Y.,

assignor to Radio Corporation of America, a corporation of Delaware Application May 11, 1938, Serial No. 207,193 6 Claims. (Cl. 250-427) My present invention relates to rectifiersgenin the plate circuit. That is, the voltage across erally, but in particular to a rectifier having a M is approximately Ep-I-[LEg where Ep is the characteristic whose slope is less for a range of peak voltage across coil 4, Eg is the peak voltage large input voltages than for lesser voltages. across coil 5, and ,l is the amplification factor An object of the invention is to obtain, from of the tube. 5

2. single rectifier tube, a direct voltage for auto- For signals in the range where E is greater matic volume control of a preceding amplifier, than the voltage of source l2,however, the action and detection of modulated radio frequency curis substantially different. With suitably large rent, with a detection characteristic which is values of condenser HI and resistor II, the in- 10 relatively fiat for strong signal input voltages. stantaneous potential of grid 1 swings to sub- 10 In the drawing: stantially zero on the positive peak of each wave, Fig. 1 shows an arrangement in accordance regardless of the amplitude of the wave so lon with the invention, and as Eg is greater than the voltage of source I2.

Fig. 2 shows an alternative form of the ar- H me h p k f h voltage W v pp .15 rangement of Fig. 1, in the plate circuit, the voltage applied, Ep, minus Referring to Fig, 1, tube l is an amplifier of the drop across resistor I4 plus the Voltage of radio frequency signals impressed on its tuned ourmust d p to a y Small Positive input circuit l' by a si nal sour e ot, ho n. value to be consistent with the drawing of only The tuned output coil 3 of tube is coupled to a m l amount f pl current at each p coil 5 connected in the grid circuit of detector e v p ak- H n e h voltage cr ss r tube 9, and, with like polarity, to coil 4 in the s r I4 m be ppr x y q l to E1 p plate circuit of 9-. A load resistance ll is included h v l ge f source t. The r e of h n e of in the grid circuit of tube 9 and the grid return t e voltage across resistor M with resp to of tube 1 is connected through filter resistor 2 Variation of signal intensity is thus smaller than to the negative end of load resistor H so that in the s Of W Signals in the ratiO 9 to 25 direct voltage produced by rectification of signal Ep+; Eg). Roughly speaking, it may be said current in the grid circuit of tube 9 is impressed t for W a Signals S that no id c cu on the grid of tube l to control its amplification ifi a n o the signal v l pp in accordance with the input signal level imin the grid circuit is effectively transferred, with pressed on detector 9. A source of D. c. potena multiplication in efieotiveness M, to the plate tial i2 i al o onn ted i the grid ir it f circuit with the result that the plate circuit rectitube 9 with its negative terminal towards the fioation i greatly i pr ved r w k i nal grid 1 to provide a threshold level below which While f r strong signals the voltage mp e e rectification does not occur in the grid circuit. on the grid p es t Own ect fication and Th numeral :0 d t th u l R, F, by-pass leaves the plate circuit rectification to its own condenser across load, I l. devices. Thus not only is the input voltage to In the plate circuit of tube 9 a load resistance the detector d ac by au o atic Volume 00n- I4, shunted by R, F, by-pass cond n I3, i trol action, but the output of the detector is also connected in series with a source of D. C. voltlimited to a m h e gr dual increase with 4 age It whose positive terminal is toward plate 8. Signals of large amplitude The ratio of E1) o a Preferably the voltage of source I8 is equal to may be Varied Obtain the best results for y the voltage of source 12 multiplied by the ampli- Particular purpose e foregoing d scussion has fication factor or the tube. With this adjustment been directed to direct currents p u d y unthe action of the circuit on weak signals is as modulated signals, but ase Of m dulation of follows: so long as the peak voltage across coil 5 y t the V a on of the direct current 45 i l s tha th Voltage f bi source l2 no through resistance 54 constitutes a modulation rent flows in the grid circuit of tube 9 and the f q y v l w i h is ran ferr d hrou h a plate circuit behaves as though the tube were blocking n s r E to y esir d form of a diode with an impressed R. F. voltage eq l utilization circuit as indicated by the legend in to the voltage of coil 4 plus the voltage of coil 50 5 multiplied by the amplification factor of the The circuit of Fig. 2 differs from that shown in tube. With suitably large values of resistance Fig- 1 o y in that the o d esistances H and i4 and condenser l3, this results in a direct volt- M are each Connected across both its esp ndage across resistance M which is substantially ing by-pass condenser, Ill or l3, and also across 55 equal to the total effective peak voltage applied the R. F. voltage-input. This modification is well 55 known per se in detector circuits, and need not be further described. The advantage of the arrangement of Fig. 2 is that a single input coil divided by a tap point into sections 4 and 5 may be used, instead of separate coils 4 and 5 insulated from each other as in Fig. 1. The action of Fig. 2 is in all other respects the same as explained in connection with Fig. 1.

While I have indicated and described several systems for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particu lar organizations shown and described, but that many modifications may be made without departing from the scope of my invention, as set forth in the appended claims.

What I claim is:

1. A rectifier circuit comprising in combination an electron discharge tube having. a cathode and two auxiliary electrodes so arranged in a single electron stream from the cathode that electron flow to one of said electrodes is strongly influenced by the potential of the other electrode, an external load circuit connected between each of said electrodes and cathode thereby to provide a pair of rectifier circuits, means for applying solely unrectified high frequency alternating voltage in each of said rectifier circuits, means for applying a positive direct voltage to one of said electrodes, and a utilization device connected to one of said load circuits.

2. A rectifier circuit comprising in combination an electron discharge tube having a cathode and two auxiliary electrodes so arranged that electron flow to one of said electrodes is strongly influenced by the potential of the other electrode, an external load circuit connected between each of said electrodes and cathode thereby to provide a pair of rectifier circuits, means for applying solely unrectified high frequency alternating voltage in each of said rectifier circuits, means for applying a positive direct voltage to one of said electrodes, means for applying a negative potential to the other of said electrodes, and a utilization device connected to one of said load circuits.

3. A rectifier circuit as defined in claim 2, wherein said negative potential means has a magnitude such as substantially to cut ofi the fiow of current to the electrode at the positive potential.

4. A rectifier circuit for supplying automatic volume control potential and audio frequency currents from a modulated wave, comprising in combination an electron discharge tube having a cathode and two auxiliary electrodes so arranged that electron flow between said cathode and one of said electrodes is strongly influenced by the potential of the other of said electrodes, an audio output circuit and a source of positive direct voltage connected between said cathode and said one electrode, a load circuit including a resistance and a source of negative potential connected between cathode and said other electrode, means for applying solely unrectified modulated waves to said two electrodes, and a circuit connected to said last named load circuit for utilizing direct potentials thereacross.

5. In combination, in a radio receiver, a detector tube provided with at least a cathode, an output electrode and a control grid therebetween, a modulated carrier voltage input circuit connected between the grid and cathode and including a load impedance in circuit for developing a unidirectional voltage from rectified carrier voltage, a second modulated carrier voltage input circuit connected between the output electrode and cathode and including a second load impedance in circuit therewith, means establishing said output electrode at a positive potential relative to the grid and cathode, and independent voltage utilization circuits connected to said load impedances.

6. In combination, in a radio receiver, a detector tube provided with at least a cathode, an output electrode and a control grid therebetween, a modulated carrier voltage input circuit connected between the grid and cathode and including a load impedance in circuit for developing a unidirectional voltage from rectified carrier 'volt- 7 age, means for establishing said grid at a negative potential relative to cathode, a second modulated carrier voltage input circuit connected between the output electrode and cathode and including a second load impedance in circuit there-- with, means establishing said output electrode at a positive potential relative to the grid and cath-' ode, and independent voltage utilization circuits connected to said load impedances.

ROY A. WEAGANT. 

